1. Field of Invention
The invention relates to digital data transmission, and, more particularly, to apparatus and methods for data rate matching of transmissions in a telecommunications system.
2. Discussion of Related Art
Telecommunications systems must often accommodate mismatched data rates of different portions of the telecommunications pathway. For example, a transmitting unit may produce data having a different bit rate than the bit rate associated with a communication transiting a transmission medium. To accommodate the data rate mismatch, data delivered to the transmission medium has its rate modified to accommodate that required by the transmission medium. Similarly, data received from the transmission medium has its rate modified to that required for processing by a receiving unit. These processes of data rate conversion are typically called rate matching and de-matching respectively for a first data rate conversion process and a second conversion process that restores the original data rate.
Rate matching is commonly employed in mobile telephone communications systems. Such systems typically entail standards that affect rate matching processes, which in turn are established by industrial standards organizations. For example, in Europe, the European Telecommunications Standards Institute (ETSI) had original responsibility for the Universal Mobile Telecommunication System (UMTS) standardization process. In 1998, the Third Generation Partnership Project (3GPP) was formed to continue technical specification work, in part related to channel coding and multiplexing.
In the UMTS, higher layers assign a rate-matching attribute for each transport channel, and the attributes are changed through higher layer signaling. Knowledge of an attribute is used to calculate a number of bits to be repeated or punctured (removed) for a rate matching process. Moreover, the bit rate on a transport channel can vary between transmission time intervals.
For example, during an uplink transmission, a total bit rate after transport channel multiplexing is matched to a total channel bit rate of allocated dedicated physical channels. During an uplink, puncturing or repeating is performed to match the coded composite transport channel bit rate to the physical channel bit rate. Unfortunately, processing of data to change its bit rate can lead to inefficiencies in communication, such as transmission delay.